Citing anonymous sources, the agency claims this has resulted in the appearance of graffiti proclaiming “Pyongyang speed is drug speed” and referring to the workers as “drug troops”.

Michael Probst/AP
Crystal meth is allegedly being supplied to construction workers in North Korea (file picture)

The building projects, which include a 70-storey high rise apartment block and at least 60 other structures, are on a tight deadline to be completed before the weather gets too cold, the source added.

It also reports the daubings are being treated as a political offence within the notoriously secretive Communist state, with police officers now searching for those responsible.

Phil Robertson, Asia director for Human Rights Watch, told Huffington Post UK: “If the North Korean government really wants these people to work faster, they should try paying them for a change.

“The fundamental problem is forced labor is being using in a systematic and pervasive way across the country on just about every project that Kim Jong-Un and the other leaders deem a priority, causing incredible suffering to the North Korean people.

“If it’s true that they are now force feeding them speed to prevent the workers from collapsing, this is a new low even for North Korea.”

In January 1942, one letter from a medical officer says that he used the drug after troops became surrounded by Russians and were attempting to escape in sub zero temperatures. “I decided to give them Pervitin as they began to lie down in the snow wanting to die,” wrote the officer.

“After half an hour the men began spontaneously reporting that they felt better.

“They began marching in orderly fashion again, their spirits improved, and they became more alert.”

But the drug comes with horrendous side effects. Aside from dizziness, depression, sweating and hallucination, some soldiers died of heart failure while others who shot themselves in a psychotic haze.